The inheritance of days to flowering in broccoli (Brassica oleracea var. italica)

Summary Crosses between an early flowering inbred broccoli (Brassica oleracea L. var. italica) HS140 and four later maturing inbred lines, S301, S310, s318, and S258, were studied to determine the inheritance of earliness as expressed by days to first open flower. Mean days to first flower for F₁ and F₂ were almost identical, and were close to the mean of the two parents in three crosses, indicating additive inheritance. In the cross HS140×S258, for which no F₁ plants were available, the F₂ mean was closer to the mean of the early parent, but this was likely due to a distortion of the data caused by the very late maturation of S258, the latest maturing parent in the study. Frequency distribution for parents and progenies supported the conclusions from parent and progeny mean values and indicated that days to maturity is a quantitative character, with mostly additive inheritance.Oregon Agricultural Experiment Station Technical Paper No. 7578.     

Segregation for heading date and stem enlargement in kohlrabi x broccoli crosses

Summary F₁ and F₂ progenies from crosses of an early broccoli (Brassica oleracea var. italica L.) line with kohlrabi (B. oleracea var. gongyloides) indicated that days to flower bud maturity in annual segregates is quantitative and additive in inheritance. It appeared that the biennial kohlrabi parent strongly contributed genetic factors for late maturity. F₁ plants of both crosses, 98% of F₂ plants from early broccoli × kohlrabi, and 81% of the F₂ plants from late broccoli × kohlrabi were annual in 1980. In 1986, 96% of early broccoli × kohlrabi F₂ and 87% of late broccoli × kohlrabi F₂ plants were annual. Kohlrabi stem enlargement showed a continuous range of expression in the F₂ with some dominance of broccoli type. Few F₂ plants were close to the kohlrabi parent in degree of stem enlargement.     

Inheritance of drought resistance related traits in two crosses of groundnut (<Emphasis Type="Italic">Arachis hypogaea</Emphasis> L.)

Groundnut (Arachis hypogaea L.) is an important oilseed crop grown in more than 100 countries across wide range of environments. Frequent occurrence of drought is one of the limiting factors adversely affecting groundnut productivity, especially in rainfed areas, and hence genotypes having high water use efficiency (WUE) under limited available water need to be developed. In groundnut, WUE is correlated with SPAD chlorophyll meter reading (SCMR) and specific leaf area (SLA). These two traits, SCMR and SLA, can be used as surrogate traits for selecting for WUE. In order to improve SCMR and SLA, and in turn WUE in groundnut, a good knowledge of the genetic system controlling the expressions of these traits is essential for the selection of the most appropriate and efficient breeding procedure. The present investigation was conducted to determine the gene action controlling the inheritance of SCMR and SLA in two crosses, ICG 7243 × ICG 9418 and ICG 6766 × Chico, and their reciprocals. Six generations of each cross (P₁, P₂, F₁, F₂, BC₁P₁, and BC₁P₂) were evaluated for SCMR and SLA at two stages of the crop growth viz., 60 and 80 days after sowing (DAS). For SCMR at 80 DAS, additive effects were important in both the crosses whereas predominance of dominance effects with duplicate epistasis was observed for SCMR at 60 DAS and SLA at both stages in both the crosses. Predominance of additive effect for SCMR at 80 DAS suggested effective selection could be practiced even in early generations whereas for SCMR at 60 DAS and SLA at both stages in both crosses, it would be better to defer selection to later generations. Further, recording of SCMR and SLA should be done between 60 and 80 DAS for screening the germplasm lines for drought tolerance.     

Genetic basis of pod borer (Helicoverpa armigera) resistance and grain yield in desi and Kabuli Chickpea (Cicer arietinum L.) under unprotected conditions

A series of half-diallel crosses involving early, medium and late maturity desi and kabuli type chickpea (Cicer arietinum L.) genotypes with stable resistance to Helicoverpa pod borer, along with the parents, were evaluated at two locations in India to understand the inheritance of pod borer resistance and grain yield. Inheritance of resistance to pod borer and grain yield was different in desi and kabuli types. In desi type chickpea, the additive component of genetic variance was important in early maturity and dominance component was predominant in medium maturity group, while in the late maturity group, additive as well as dominance components were equally important in the inheritance of pod borer resistance. Both dominant and recessive genes conferring pod borer resistance seemed equally frequent in the desi type parental lines of medium maturity group. However, dominant genes were in overall excess in the parents of early and late maturity groups. In the kabuli medium maturity group, parents appeared to be genetically similar, possibly due to dispersion of genes conferring pod borer resistance and susceptibility, while their F₁s were significantly different for pod borer damage. The association of genes conferring pod borer resistance and susceptibility in the parents could be attributed to the similarity of parents as well as their F₁s for pod borer damage in kabuli early and late maturity groups. Grain yield was predominantly under the control of dominant gene action irrespective of the maturity groups in desi chickpea. In all the maturity groups, dominant and recessive genes were in equal frequency among the desi parental lines. Dominant genes, which tend to increase or decrease grain yield are more or less present in equal frequency in parents of the early maturity group, while in medium and late maturity groups, they were comparatively in unequal frequency in desi type. Unlike in desi chickpea, differential patterns of genetic components were observed in kabuli chickpea. While the dominant genetic component was important in early and late maturity group, additive gene action was involved in the inheritance of grain yield in medium duration group in kabuli chickpea. The dominant and recessive genes controlling grain yield are asymmetrically distributed in early and medium maturity groups in kabuli chickpea. The implications of the inheritance pattern of pod borer resistance and grain yield are discussed in the context of strategies to enhance pod borer resistance and grain yield in desi and kabuli chickpea cultivars.     

Genetic analysis in Chrysanthemum morifolium. I. Flowering time and flower number at low and optimum temperature

Summary The number of days to flowering and the number of flowers per plant were studied at 12, 13, 15 and 17 C night temperature in 79 F₁ populations from 15 parents. Only a few F₁ plants flowered earlier than their parents; the majority flowered at the same time, later or not at all. The number of flowers of the F₁ plants was higher than that of the parents.Genetic analyses showed a broad sense heritability of 70% for days to flowering and flower number and a highly significant GCA effect for days to flowering.The progenies and parents that flowered early at one temperature were generally early at all temperatures.     

Sources and inheritance of earliness in tropically adapted indeterminate common bean

Summary Nineteen early maturing, indeterminate common bean parents were crossed with a tester line of normal maturity. All parents, F₁ hybrids, F₂'s, and backcross generations were evaluated at CIAT-Palmira, Colombia. All 19F₁ populations flowered and matured almost as early as the respective early parent (mean of 61 vs 59 days). The F₂ populations were slightly less early (63 days), but were still earlier than the mean of the two parents (65 days). Additive effects for days to maturity were usually larger than dominance or interaction effects. Narrow sense heritability for days to flower and maturity were high (greater than 0.67), while heritabilities of absolute and relative duration of pod filling were low (0.17 to 0.50). Also, our data indicated that for each day of increase in earliness, yield potential will decrease 74 kg/ha.     

Relationship of plant height and days to maturity with resistance to spot blotch in wheat

A total of 1,407 spring wheat (T. aestivum) lines of Indian and CIMMYT (International Maize and Wheat Improvement Centre, Mexico) origin were evaluated for plant height, days to maturity and resistance to spot blotch (caused by Bipolaris sorokiniana) during the 1994–95, 1995–96 and 1996–97 crop seasons. The frequency distribution of genotypes, based on disease score ignoring the growth stages, differed from the distribution in which disease score was assessed on a similar growth stage. Two crosses each,between `tall resistant × dwarf susceptible' and `late resistant × early susceptible' genotypes, were made. The evaluation of homozygous resistant lines in the F₃, F₄ and F₅ generations of both crosses showed a wide range of plant height and days to maturity. These lines showed significant differences for plant height and days to maturity but did not show a significant difference for AUDPC values of spot blotch. The correlation coefficients for AUDPC versus plant height or days to maturity were weak, i.e., – 0.336 and 0.061, respectively. Results indicated that resistance to spot blotch severity was independent of plant height and days to maturity in progenies from these crosses.     

Mid-parent heterosis and combining ability of European corn borer resistance in maize

Success in breeding maize resistant to the European corn borer has been limited, with the exception of leaf feeding resistance. The inheritance of resistance to leaf, sheath-collar and ear damage in four maize germplasms and their six F₁ crosses was evaluated by diallel analysis. Plants in a completely randomized design were artificially infested at the whorl, anthesis or full silk stage of plant development and were evaluated in the field for insect damage. A damage index based on size, number and location of lesions was calculated for each stage. Stowell's Evergreen (susceptible) had a mean damage index three to six times that of Maiz Amargo (resistant) at the whorl stage and the progeny plants were more resistant than the susceptible parent. Maiz Amargo and its crosses had significantly lower mean indices than Stowell's Evergreen for sheath-collar damage in Year 1 but not Year 2. Zapalote Chico, Maiz Amargo and their cross were significantly less damaged than other genotypes at the full silk stage. Heterosis values indicated an increase in resistance of crosses over the midparent average at all three stages of development. General combining ability (GCA) was highly significant for all types of damage, but specific combining ability was significant only for leaf damage. Based on estimates of GCA, Maiz Amargo was the best source of resistance to leaf and sheath-collar damage and both Zapalote Chico and Maiz Amargo would be good parents for ear damage resistance. Results suggest that resistance at different plant development stages can be combined.     

Reciprocal cross differences in a 6×6 diallel set of groundnut (Arachis hypogaea L.) in the F1 generation

Summary Reciprocal cross differences were studied in a 6×6 diallel full set comprising of thirty hybrid combinations of groundnut in the F₁ generation.Reciprocal cross differences were observed for growth habit in four pairs of crosses, for leaf colour, flower colour and stem pigmentation in two pairs of crosses each. It was observed that the inheritance of flower colour, stem pigmentation and testa colour which exhibited different shades of purple colour was likely to be governed by pleiotropic gene(s). Among the quantitative characters significantly positive reciprocal effects were observed in different crosses for number of mature pods per plant, weight of pods per plant and shelling percent. Marked reciprocal cross differences were observed for pod and kernel characters like pod filling, pod beak, pod constriction and testa colour.     

Inheritance of duration from sowing to first flowering in pigeonpea

Duration from sowing to flowering is the most important trait influencing adaptation in pigeon pea (Cajanus cajan), but the inheritance of this trait has not been elucidated clearly. Crosses were made between two early (60 to 70d) and one late (160 to 170d) flowering pigeonpea genotype and F₁, F₂ and BC₁ populations produced. These populations, comprising 60 to 100 parents, 30 F₁, 400F₂ and 40 to 50 BC₁ plants, were grown under natural (mean13.4 hd^-1) and artificially extended (to 15 hd^-1) daylength and duration from sowing to first flowering recorded. Genetic analysis of the segregation ratios, supported by Chi-square tests, indicated that the duration from sowing to flowering in each of the crosses was controlled by two genes assorting independently and with predominantly additive quantitative effects. The segregation patterns were most clearly defined in the 15 hd^-1 daylength. This revised version was published online in July 2006 with corrections to the Cover Date.     

The inheritance of curding periods in early summer and autumn cauliflower

Two series of diallel crosses were made between (a) eight varieties of autumn cauliflowers and (b) six inbred lines from a single variety of early summer cauliflowers in order to study the inheritance of curding periods. F₁'s and parents from each diallel were grown in separate randomised block experiments and the analyses presented as conventional Wr Vr graphs.The array points from the diallel analysis of autumn cauliflowers were spread along a regression line of unit slope thus indicating that the gene system controlling curding periods was additive with no evidence of gene interaction in these crosses. Varieties of early/mid period maturity with the exception of Veitch's Autumn Giant possessed most dominant polygenes while late maturity was controlled by recessive polygenes. The diallel analysis of curding periods for the early summer cauliflower inbreds indicated the presence of some interaction which was due to the influence of two lines. On reanalysis without these lines the regression of Wr Vr agreed with a slope of 1, although there was a higher degree of dominance than was shown by the autumn cauliflowers. Analysis of the early summer cauliflower lines for numbers of leaves produced before curding indicated an association between low leaf numbers and early curding, and between high leaf numbers and late curding.None of the F₁ hybrids in either series of crosses curded earlier than the earlier curding parent.     

Genetical studies of quantitative characters in peas. 2. A six-parent diallel cross of cultivars and primitive forms

Summary Results from the F₁ generation of a set of 6×6 full diallel crosses involving representatives of wild forms, primitive and European cultivars are described. The aim was to compare the systems of genetic control in the parents used in the present experiment with those known to operate in a number of contemporary cultivars. The plant characters analysed were days to and node of first flower, internode length, number of flowers per node and number of ovules per pod.Different systems of genetic control were found in some of the parents used in this experiment from those characteristic of cultivars in that dominance, and in some cases interaction, have been found to operate. The most extreme difference concerned earliness of flowering which results from an accumulation mulation of dominant alleles in primitive forms, but an accumulation of recessives in those European and North American cultivars so far analysed in detail. Only one of the characters would appear to be under a system of genetic control similar to that of cultivars, node of first flower.These results are discussed in relation to those obtained from the analyses of previous sets of diallel crosses.     

Genetic analysis in Chrysanthemum morifolium. II. Flower doubleness and ray floret corolla splitting

Summary The inheritance of flower doubleness and floret corolla shape was studied in 70 F₁ populations from 16 parents. Singleness is partially dominant over doubleness. The overall segregation for doubleness in crosses of the type double × single was 29% single, 58% semi double and 12% double. The percentages varied with the parents.The anemone flower type is inherited as if it were a single. Crosses between plants with ligulate (split lengthwise) and tubular corollas produced ligulate, tubular and intermediate types in various ratios depending on the parents used. Flower doubleness and corolla shape are not linked.     

Combining ability for seed yield traits of Chenopodium quinoa breeding lines

For a better understanding of the inheritance of seed yield traits in Quinoa (Chenopodium quinoa) Willd., a half-diallelic crossing experiment with six diverse but uniform breeding lines was conducted. True hybrid plants were detected by means of differences in panicle colour in 14 out of the 15 crosses performed. The agronomic performance of 14 F₂ populations and six parental lines was evaluated in field trials on fertile clay soil. General and specific combining ability of the lines (GCA and SCA) were estimated. Highly significant differences in GCA effects were found between the lines for plant height at maturity, early flowering, early maturity, seed yield and thousand seed weight. Significant SCA effects were only found for plant height at maturity. However, SCA effects were rather small and accounted for 7% of the total variance. The finding of large GCA effects and low SCA effects suggests that best selection results could be expected from crosses between the agronomic best performing genotypes. This revised version was published online in August 2006 with corrections to the Cover Date.     

Breeding the common bean (Phaseolus vulgaris L.) for resistance to bean common mosaic virus: alternatives to backcrossing

A series of field experiments was undertaken in order to determine whether resistance to bean common mosaic virus (BCMV) could be incorporated into genotypes of the common bean (Phaseolus vulgaris L.) suitable for cultivation in Zimbabwe without recourse to backcrossing. Six inbred genotypes carrying the resistance-conferring alleles at the loci I and Bc-3 were crossed with five locally-adapted inbred genotypes. The first experiment comprised F₃ progeny rows, each derived from a single unselected F₂ plant, the second, F₃ bulks selected for resistance, and the third, a comparison of selected and unselected F₂-derived F₄ lines. The number of days to flowering and to maturity, the incidence of mosaic and necrosis symptoms, seed yield and seed size were recorded. There was evidence that late flowering and maturity were associated with BCMV resistance in some crosses, though not strongly enough to present an obstacle to plant breeding. The incidence of virus symptoms and seed yield were influenced by genetic factors additional to the major resistance genes, and variation in seed yield was present not only between bulk populations of crosses, but also between single-row plots of lines within crosses. This indicates that early-generation selection for yield in the presence of BCMV, even among progeny selected for BCMV-resistace, is likely to be effective. However, the variation in yield among F₄ lines was least in the highest-yielding crosses, which may represent a limit to successful selection for yield. Seed size was partly under additive genetic control, but there was also evidence of non-allelic interactions. There was no association between large seed size, preferred by consumers, and susceptibility to BCMV in the progeny, indicating that the association between these characters in the parent lines is fortuitous and will not present an obstacle to plant breeding. It is noted that a considerable amount of useful genetic information can be obtained without recourse to elaborate crossing schemes, provided that unselected progeny are included in experiments as controls. The evidence presented indicates that resistance to BCMV can be combined with appropriate values of maturity date, yield and seed size without the need for backcrossing.     

Genetic analysis of thrips resistance in cowpea (<Emphasis Type="Italic">Vigna unguiculata</Emphasis> [L.] Walp.)

Flower bud thrips, Megalurothrips sjostedti is the most severe field pest of cowpea that causes massive flower abortion which eventually results to substantial yield reduction in Africa. There is paucity of information on the mode of gene actions controlling inheritance of resistance to flower bud thrips in cowpea in the literature. The objectives of study were to assess the genetic variability for thrips resistance among the cowpea germplasm, determined the mode of inheritance of genes that conferred resistance and both broad and narrow-sense heritability estimates for the inheritance of thrips resistance in cowpea. Twelve cowpea lines were used in crosses in the screen house at IITA, Ibadan. The mating was accomplished using North Carolina design II to generate 48F₁ hybrids, which were eventually evaluated with the parents. Data on number of peduncles, number of pods and number of thrips per flower were recorded and subjected to analysis of variance using random model by SAS 9.2. Significant variability was observed for most agronomic and thrip-adaptive traits among the cowpea germplasm, parental-lines and F₁ genotypes evaluated. General combining ability (GCA) and specific combining ability (SCA) mean squares were significant (P < 0.01) for number of pods per plant and other traits under the research environment. The GCA effect accounted for 68.82–80.07% of the total variation among hybrids for all traits except days to flowering; SCA explained less than 50% of the total variation. Narrow-sense heritability estimates ranged from 7.53 (days to flower) to 63.92% (number of peduncles per plant). Additive gene action largely controlled the inheritance of yield components and other traits under thrips infestation and these traits were moderately heritable.     

Inheritance of temperature sensitivity of the photoperiod response in common bean (Phaseolus vulgaris L.)

Summary Photoperiod response of flowering in common bean (Phaseolus vulgaris L.) is thought to be controlled by the genes Ppd and Hr. However, cultivars also vary in the degree that cooler temperatures reduces their sensitivity to photoperiod. To examine the inheritance of this temperature sensitivity, crosses of cvs. Gordo x de Celaya and Flor de Mayo × Rojo 70 were evaluated at two sites differing in mean temperature and using 12.5-h natural photoperiod or 18-h artificially extended photoperiod. Under 18-h photoperiod at the warmer site, Palmira, no plants of the parents or of the F₂ populations flowered, confirming that the parents were sensitive to photoperiod. Under 12.5-h photoperiod at the cooler site, Popayan, the parents for each cross flowered at similar dates and no segregation for days to flower was observed. However, under 18-h photoperiod, de Celaya and Rojo 70 and the F₁ populations did not flower within 100 days after planting, while the F₂ and F₃ populations showed segregation that was consistent with single gene inheritance, late flowering being dominant. Late flowering at Popayan under 18-h photoperiod indicates a lack of temperature sensitivity, so temperature insensitivity of the photoperiod response was dominant to sensitivity. The name Tip, for temperature insensitivity of photoperiod response, is proposed for this gene, with the recessive form of this gene conditioning earlier flowering at cooler temperatures with long daylengths. It is recognized that the observed segregation patterns could represent the effect of multiple alleles at the Ppd or Hr loci, and studies are proposed to test this possibility with molecular markers and recombinant inbred lines.     

Inheritance of bolting tendency in lettuce Lactuca sativa L.

Resistance to early flowering is an important attribute of lettuce cultivars adapted to tropical conditions. Lettuce cultivars may vary widely in the number of days necessary from sowing to inflorescence formation and flowering. In this paper, we report on the polygenic inheritance of the number of days to flowering in two crosses among contrasting lettuce cultivars – Vitória × Brasil-303 and Babá × Elisa. F₁ and F₂ seed were obtained for each cross, and used to estimate broad sense heritabilities. F₃ families were obtained from randonly sampled F₂ plants, and used to estimate narrow sense heritabilities based on parent-offspring regression. Trials were carried out in plastic greenhouses in Campos dos Goytacazes, in the Northern part of the State of Rio de Janeiro, Brazil. Broad and narrow sense heritabilities for days to first anthesis were 0.737 and 0.489 for the cross Vitória × Brasil-303, and 0.818 and 0.481 respectively, for the cross Babá × Elisa. In both crosses, both early and late-flowering transgressive segregants were obtained. Genetic gains based on selection of late flowering transgressive segregants in the F₂'s were estimated to be 10.2 days in Vitória × Brasil-303 cross, and 8.7 days in the Babá × Elisa cross. This revised version was published online in August 2006 with corrections to the Cover Date.     

Inheritance of neurotoxin (ODAP) content, flower and seed coat colour in grass pea (Lathyrus sativus L.)

Summary A strong epidemiological association is known to exist between the consumption of grass pea and lathyrism. A neurotoxin, -N-Oxalyl-L-, -diaminopropanoic acid (ODAP) has been identified as the causative principle. This study was undertaken to investigate the mode of inheritance of the neurotoxin ODAP, flower and seed coat colour in grass pea. Five grass pea lines with low to high ODAP concentration were inter-crossed in all possible combinations to study the inheritance of the neurotoxin. Parents, F₁ and F₂ progenies were evaluated under field condition and ODAP analyzed by an ortho-phthalaldehyde spectrophotometric method. Many of the progenies of low x low ODAP crosses were found to be low in ODAP concentration indicating the low ODAP lines shared some genes in common for seed ODAP content. The F₁ progenies of the low ODAP x high ODAP crosses were intermediate in ODAP concentration and the F₂ progenies segregated covering the entire parental range. This continuous variation, together with very close to normal distribution of the F₂ population both of low x low and low x high ODAP crosses indicated that ODAP content was quantitatively inherited. Reciprocal crosses, in some cases, produced different results indicating a maternal effect on ODAP concentration. Blue and white flower coloured lines of grass pea were inter-crossed to study the inheritance of flower colour. Blue flower colour was dominant over the white. The F₂ progenies segregated in a 13:3 ratio indicating involvement of two genes with inhibiting gene interactions. The gene symbol LB for blue flower colour and LW for white flower colour is proposed.     

Analysis of genetic architecture for some physiological characters in sesame (<Emphasis Type="Italic">Sesamum indicum</Emphasis> L.)

Combining ability for some important physiological parameters in sesame were examined to understand the nature of gene action and to identify parents for breeding programme. Seven diverse genotypes of sesame, their 21 F₁s and 21 F₂s were grown in summer, 2003, in a randomized complete block design with three replications. Data were collected on leaf area index (LAI) at 30, 45, 60 and 75 days after sowing (DAS), crop growth rate (CGR) estimated between 30–45 DAS, 45–60 DAS and 60–75 DAS, days to peak flowering (DPF), duration of flowering (DF), duration from peak flowering to maturity (DFM), oil content in percentage (OC) and oil yield (OY) plant⁻¹. Analysis of combining ability was done on the above physiological characters following Method-2, Model-I of Griffing (Aust J Biol Sci 9:463–493 1956). Variances due to general combining ability (GCA) and specific combining ability (SCA) for all the physiological traits were highly significant in both F₁ and F₂ generations indicating importance of both additive and non-additive gene actions for the inheritance of all the physiological characters in both F₁ and F₂ generations. Preponderance of non-additive gene action was recorded for CGRs, LAI 3, LAI 4, DPF, DF and OY in both the F₁ and the F₂ generations. For OC additive gene action was predominant in F₁ while non-additive gene action in F₂. The genotype OS-Sel-2 appeared as best overall general combiner in both the F₁ and the F₂ generations. For DPF, DF and DFM, the variety B 67 was best general combiner, followed by CST 2002, which could be utilized for developing early flowering and early maturing lines with determinate growth habit. Association between GCA-effects and mean performance of the parents suggested that the performance per se could be a good indicator of its ability to transmit the desirable attributes to its progenies. Crosses CST 2002 × TKG 22, CST 2002 × MT 34, MT 34 × AAUDT 9304-14-4, AAUDT 9304-14-4 × B 67, TKG 22 × Rama and TKG 22 × B 67 which showed high SCA-effect for OY, also exhibited positive and significant SCA-effects for other physiological component characters in F₁ generation. The overall results indicated that crosses CST 2002 × TKG 22 and MT 34 × AAUDT 9304-14-4 could be utilized for development of high oil yielding hybrids. The crosses OS-Sel-2 × AAUDT 9304-14-4, AAUDT 9304-14-4 × B 67 and MT 34 × OS-Sel-2 could be promising for isolation of superior recombinants for high oil yield coupled with early maturity and other growth characters in advanced generations of segregation. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.